How to create a college listing website using wordpress?

Hello,
I don't know the theme listeo and the possibilities it gives you to achieve your goal.

But if I had to do this I probably would use a Website Builder like Bricks Builder, Oxygen Builder, Breakdance Builder, Elementor in Combination with ACF, CPT UI or Meta Box Plugin .

Btw. check your (perma)slug settings I assume something is wrong with it... thats why you get the 404 error page